1. Field of the Invention
The present invention relates to a lens frame unit for preventing fogging of an optical member disposed at a distal end and an endoscope including this lens frame unit.
2. Description of the Related Art
Generally, medical endoscopes such as a rigid scope and a flexible scope for being inserted into a body cavity to perform observation or treatment of the inside of the body cavity, and industrial endoscopes for performing inspection or repair in a plant facility are widely used. With such endoscopes, based on an image that is of an object to be observed and is formed on an eyepiece optical system or an imaging unit by an optical member of an objective optical system disposed at a distal end of the endoscope, desired treatment or inspection, for example, is performed.
When an endoscope is inserted into a humid environment such as in a body cavity, if the temperature of the inserted endoscope is lower than the temperature of the environment, fogging due to the temperature difference may occur on an optical member at a distal end of the endoscope, such as on a surface of a lens cover.
To deal with such fogging, for example, Japanese Patent No. 4616421 discloses an endoscope including an anti-fogging unit for preventing fogging of an optical member disposed at a distal end of the endoscope. In this endoscope, behind a lens cover housed in a cylindrical lens frame, a heater formed in a ring shape is arranged. Energizing a heater in advance to heat the lens cover at an appropriate temperature, and then inserting the endoscope into a body cavity, for example, prevent fogging of a surface of the lens cover.